Substrate buffer structure for group III nitride devices
View Patent ↗A semiconductor photonic device and associated method are disclosed. The device includes a substrate and a buffer structure on the substrate. The buffer structure is formed of a discontinuous layer of aluminum gallium nitride and a gallium nitride layer on the aluminum gallium nitride layer having a thickness that functionally minimizes the number of defects propagated through it. At least two doped Group III nitride layers are on the buffer structure, with the layers being of opposite conductivity type from one another for providing electrons and holes that combine to generate an emission from the device when current is applied to the device.
1. A semiconductor photonic device comprising:
a conductive silicon carbide substrate;
a buffer structure on said conductive silicon carbide substrate formed of a discontinuous aluminum gallium nitride layer and a continuous gallium nitride layer directly on said discontinuous aluminum gallium nitride layer, said continuous gallium nitride layer having a thickness that functionally minimizes the number of defects propagated through it;
said discontinuous aluminum gallium nitride layer having a mole fraction of aluminum large enough to facilitate initial nucleation of said discontinuous aluminum gallium nitride layer on said substrate but less than an amount that would cause a continuous layer of aluminum gallium nitride to form; and
at least two doped Group III nitride layers on said buffer structure, said layers being of opposite conductivity type from one another for providing electrons and holes that combine to generate an emission from said device when current is applied to said device.
2. A photonic device according to claim 1 further comprising a dielectric layer on the top portions of said doped Group III nitride layers.
3. A photonic device according to claim 2 wherein said dielectric layer comprises silicon nitride.
4. A photonic device according to claim 1 having a vertical orientation with an ohmic contact to one of said doped layers and another ohmic contact to said conductive silicon carbide substrate.
5. A photonic device according to claim 1 further comprising a superlattice above said buffer structure for encouraging and supporting favorable crystal growth and better transitions between and among the layers of said device.
6. A photonic device according to claim 1 further comprising a quantum well above said buffer structure for increasing the efficiency of the device by progressively collecting the carriers in the quantum well.
7. A photonic device according to claim 1 further comprising a multiple quantum well above said buffer structure for increasing the efficiency of the device by progressively collecting the carriers in the quantum well.
8. A device according to claim 1 wherein the mole fraction of aluminum is between about 0.02 and 0.30.
9. A device according to claim 1 wherein the mole fraction of aluminum is about 0.10.
10. A device according to claim 1 wherein said discontinuous aluminum gallium nitride layer is sufficiently thick to provide a surface discrimination between itself and said substrate with respect to the nucleation of gallium nitride but less than the thickness that would mimic a full aluminum gallium nitride epitaxial layer.
11. A device according to claim 1 in which said discontinuous aluminum gallium nitride layer is between about 500 and 10,000 angstroms thick.
12. A device according to claim 1 wherein said discontinuous aluminum gallium nitride layer has a thickness of about 1500 angstroms.
13. A device according to claim 1 wherein said continuous gallium nitride layer has a thickness of a between about 5,000 and 50,000 angstroms.
14. A device according to claim 1 wherein said continuous gallium nitride layer has a thickness of about 25,000 angstroms.
15. A semiconductor photonic device comprising:
a substrate selected from the group consisting of sapphire and gallium nitride;
a buffer structure on said substrate formed of a discontinuous aluminum gallium nitride layer and a continuous gallium nitride layer directly on said discontinuous aluminum gallium nitride layer, said continuous gallium nitride layer having a thickness that functionally minimizes the number of defects propagated through it;
said discontinuous aluminum gallium nitride layer having a mole fraction of aluminum large enough to facilitate initial nucleation of said discontinuous aluminum gallium nitride layer on said substrate but less than an amount that would cause a continuous layer of aluminum gallium nitride to form; and
at least two doped Group III nitride layers on said buffer structure, said layers being of opposite conductivity type from one another for providing electrons and holes that combine to generate an emission from said device when current is applied to said device.
16. A photonic device according to claim 15 further comprising a dielectric layer on the top portions of said doped Group III nitride layers.
17. A photonic device according to claim 16 wherein said dielectric layer comprises silicon nitride.
18. A photonic device according to claim 15 further comprising a superlattice above said buffer structure for encouraging and supporting favorable crystal growth and better transitions between and among the layers of said device.
19. A photonic device according to claim 15 further comprising a quantum well above said buffer structure for increasing the efficiency of the device by progressively collecting the carriers in the quantum well.
20. A photonic device according to claim 15 further comprising a multiple quantum well above said buffer structure for increasing the efficiency of the device by progressively collecting the carriers in the quantum well.
21. A device according to claim 15 herein the mole fraction of aluminum is between about 0.02 and 0.30.
22. A device according to claim 15 wherein the mole fraction of aluminum is about 0.10.
23. A device according to claim 15 wherein said discontinuous aluminum gallium nitride layer is sufficiently thick to provide a surface discrimination between itself and said substrate with respect to the nucleation of gallium nitride but less than the thickness that would mimic a full aluminum gallium nitride epitaxial layer.
24. A device according to claim 15 in which said discontinuous aluminum gallium nitride layer is between about 500 and 10,000 angstroms thick.
25. A device according to claim 15 wherein said discontinuous aluminum gallium nitride layer has a thickness of about 1500 angstroms.
26. A device according to claim 15 wherein said continuous gallium nitride layer has a thickness of a between about 5,000 and 50,000 angstroms.
27. A device according to claim 15 wherein said continuous gallium nitride layer has a thickness of about 25,000 angstroms.
28. A semiconductor photonic device comprising:
a substrate;
a buffer structure on said substrate formed of a discontinuous aluminum gallium nitride layer and a continuous gallium nitride layer directly on the discontinuous aluminum gallium nitride layer, said continuous gallium nitride layer having a thickness that functionally minimizes the number of defects propagated through it;
said discontinuous aluminum gallium nitride layer having a mole fraction of aluminum large enough to facilitate initial nucleation of the discontinuous aluminum gallium nitride layer on the substrate but less than an amount that would cause a continuous layer of aluminum gallium nitride to form; and
at least two doped Group III nitride layers on said buffer structure, said layers being of opposite conductivity type from one another for providing electrons and holes that combine to generate an emission from said device when current is applied to said device.